Commit c65c7a30 authored May 29, 2014 by Jon Maxwell Committed by David S. Miller Jun 01, 2014

bridge: notify user space after fdb update

There has been a number incidents recently where customers running KVM have
reported that VM hosts on different Hypervisors are unreachable. Based on
pcap traces we found that the bridge was broadcasting the ARP request out
onto the network. However some NICs have an inbuilt switch which on occasions
were broadcasting the VMs ARP request back through the physical NIC on the
Hypervisor. This resulted in the bridge changing ports and incorrectly learning
that the VMs mac address was external. As a result the ARP reply was directed
back onto the external network and VM never updated it's ARP cache. This patch
will notify the bridge command, after a fdb has been updated to identify such
port toggling.

Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
Reviewed-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 4324be1e

net/bridge/br_fdb.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -487,6 +487,7 @@ void br_fdb_update(struct net_bridge br, struct net_bridge_port source,
		{
		struct hlist_head *head = &br->hash[br_mac_hash(addr, vid)];
		struct net_bridge_fdb_entry *fdb;
		bool fdb_modified = false;

		/* some users want to always flood. */
		if (hold_time(br) == 0)
		@@ -507,10 +508,15 @@ void br_fdb_update(struct net_bridge br, struct net_bridge_port source,
		source->dev->name);
		} else {
		/* fastpath: update of existing entry */
		if (unlikely(source != fdb->dst)) {
		fdb->dst = source;
		fdb_modified = true;
		}
		fdb->updated = jiffies;
		if (unlikely(added_by_user))
		fdb->added_by_user = 1;
		if (unlikely(fdb_modified))
		fdb_notify(br, fdb, RTM_NEWNEIGH);
		}
		} else {
		spin_lock(&br->hash_lock);

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